This invention relates to method and apparatus for forming glass fibers.
In one of its more specific aspects, this invention relates to a method and apparatus which improve the operation of fiber forming processes.
Glass fibers are conventionally formed by attentuating molten glass as filaments through orifices located in the bottom of a bushing containing molten glass. The filaments which are pulled from the bushing, are passed into contact with pre-pad sprays and, thereafter, with an applicator which coats the filaments with a size. The filaments are then passed into contact with a gathering shoe which combines the filaments into strands. The strands are collected on a collet as a package. The collet is usually located on a floor in the lower level of the fiber forming position.
A major problem in the formation of quality glass filaments lies in controlling the environment at, and directly below, the bushing. Due to the high temperatures within the forming area and the high speeds at which the filaments are drawn, air currents are established upwardly from the bushing and downwardly with the filaments. Therefore, air does not flow directly from the usual ceiling supply to the bushing and then through the floor openings. Generally, a large recirculation region exists in each position. Such air recirculation tends to introduce extraneous matter into contact with the filaments.
It is, therefore, desirable that a controlled atmosphere, including controlled flow of air, be maintained into the upper forming zone. While various air-introduction processes have been proposed, none accomplish the results of the present invention which serves to significantly reduce the number of breaks per hour of the strands at the bushing.